From: David Woodhouse <dwmw2@infradead.org>
To: paul@xen.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Paul Durrant <pdurrant@amazon.com>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org
Subject: Re: [PATCH v4 09/13] KVM: xen: automatically use the vcpu_info embedded in shared_info
Date: Tue, 19 Sep 2023 17:14:21 +0100 [thread overview]
Message-ID: <5f33490c1b9c201fba52fe146aca0cf828754129.camel@infradead.org> (raw)
In-Reply-To: <7de61c43-e88d-9c22-7e5f-2229d8c49523@xen.org>
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On Tue, 2023-09-19 at 16:47 +0100, Paul Durrant wrote:
>
> >
> > I think they look interchangeable in this case. If we *do* take them
> > both in kvm_xen_set_evtchn_fast() then maybe we can simplify the slow
> > path where it set the bits in shared_info but then the vcpu_info gpc
> > was invalid. That currently uses a kvm->arch.xen.evtchn_pending_sel
> > shadow of the bits, and just kicks the vCPU to deliver them for
> > itself... but maybe that whole thing could be dropped, and
> > kvm_xen_set_evtchn_fast() can just return EWOULDBLOCK if it fails to
> > lock *both* shared_info and vcpu_info at the same time?
> >
>
> Yes, I think that sounds like a neater approach.
>
> > I didn't do that before, because I didn't want to introduce lock
> > ordering rules. But I'm happier to do so now. And I think we can ditch
> > a lot of hairy asm in kvm_xen_inject_pending_events() ?
> >
>
> Messing with the asm sounds like something for a follow-up though.
AFAICT we can just delete the whole bloody lot. But yes, it's
definitely a later cleanup, enabled by the fact that we (will) now have
an agreed way of taking both locks at once, which I didn't want to do
in the first place.
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next prev parent reply other threads:[~2023-09-19 16:14 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-19 13:41 [PATCH v4 00/13] KVM: xen: update shared_info and vcpu_info handling Paul Durrant
2023-09-19 13:41 ` [PATCH v4 01/13] KVM: pfncache: add a map helper function Paul Durrant
2023-09-19 13:41 ` [PATCH v4 02/13] KVM: pfncache: add a mark-dirty helper Paul Durrant
2023-09-19 13:41 ` [PATCH v4 03/13] KVM: pfncache: add a helper to get the gpa Paul Durrant
2023-09-19 13:41 ` [PATCH v4 04/13] KVM: pfncache: base offset check on khva rather than gpa Paul Durrant
2023-09-19 13:41 ` [PATCH v4 05/13] KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA Paul Durrant
2023-09-19 14:20 ` David Woodhouse
2023-09-19 14:22 ` Paul Durrant
2023-09-19 13:41 ` [PATCH v4 06/13] KVM: xen: allow shared_info to be mapped by fixed HVA Paul Durrant
2023-09-19 13:41 ` [PATCH v4 07/13] KVM: xen: prepare for using 'default' vcpu_info Paul Durrant
2023-09-19 13:41 ` [PATCH v4 08/13] KVM: xen: prevent vcpu_id from changing whilst shared_info is valid Paul Durrant
2023-09-19 13:41 ` [PATCH v4 09/13] KVM: xen: automatically use the vcpu_info embedded in shared_info Paul Durrant
2023-09-19 14:18 ` David Woodhouse
2023-09-19 14:34 ` Paul Durrant
2023-09-19 15:38 ` David Woodhouse
2023-09-19 15:47 ` Paul Durrant
2023-09-19 16:14 ` David Woodhouse [this message]
2023-09-19 13:41 ` [PATCH v4 10/13] KVM: selftests / xen: set KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID Paul Durrant
2023-09-19 13:41 ` [PATCH v4 11/13] KVM: selftests / xen: map shared_info using HVA rather than GFN Paul Durrant
2023-09-19 13:41 ` [PATCH v4 12/13] KVM: selftests / xen: don't explicitly set the vcpu_info address Paul Durrant
2023-09-19 13:41 ` [PATCH v4 13/13] KVM: xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability Paul Durrant
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